Included here is the island of Sumatra and surrounding islands such as Nias, Siberut, Bangka and Belitungare

Sulawesian Forest of Ultrabasic Soils

Sulawesi has the most extensive area of ultrabasic soils in the World. Given the high concentration of heavy metals and low fertility of the these soils it is not surprising that certain areas support no more than low, scrubby vegetation, but in places, such as on Mount Konde west of Sovoaka, closed canopy forests have developed reaching heights of up to 35 m. Most of the tree species, which are often specially adapted to these conditions, usually belong to the family Sapotaceae or the genus Ficus, while other trees include Deplanchea bancana, Metrosideros petiolata and the endemic Hopea celebica (Dipterocarpaceae), Knema celebica (Myristicaeae) and Terminalia supitiana (Combretaceae). Included among the many epiphytes are species of the ferns Drynaria and Lecanopteris and the ant plants Hydnophyton and Mymecodia. These form symbiotic relationships with ants – the plants provide enlarged chambered stems for the ants, and plants benefit from the organic frass that is brought into these chambers by the ants. These relationships seem to have been engendered by the plant’s requirements for nutrients in these low fertile areas. Other endemic species associated with these soils include trees such as Gymnacranthera maliliensis, Myristica devogelii, M. ultrabasica (Myristicaceae) and Horsfieldia lancifolia (Myristicaceae), shrubs such as Gardenia celebica (Rubiaceae), and ferns like Tectaria subtriloba (Tectariaceae).

References

Meijer, W. 1976. Botanical Explorations in Celebes and Bali. National Geographic Society Research Reports, 60: 583-605.

Milliken, W. & Proctor, J. 1999. Montane forest in the Dumoga Bone National Park, Northern Sulawesi. Edinburgh Journal of Botany, 56: 449-458.

Proctor, J. 2003. Vegetation and soil and plant chemistry on ultramafic rocks in the tropical Far East. Perspective in Plant Ecology, Evolution and Systematics, 6: 105-124.

Steenis, C. G. G. J. van. 1957. Outline of the vegetation types in Indonesia and some adjacent regions. Proceedings of the Pacific Scientific Congress, 8: 61-97.

Whitmore, T. C. & Sidiyasa, K. 1986. Composition and structure of a lowland rain forest at Toraut, northern Sulawesi. Kew Bulletin, 41: 747-756.

Whitten, A. J., Mustafa, M. & Henderson, G. S. 1987. The Ecology of Sulawesi. Gadjah Mada University Press.